There are many systems designed to bring intimate mixture of the oxidizing agent, i.e. an oxygen-carrying gas such as air, and a fuel fluid, generally a liquid or gaseous hydrocarbon, prior to discharge of the resulting combustible mixture from a burner mouth. Some of these systems have been discussed in greater detail in the above-identified applications, which are hereby incorporated in their entirety by reference.
The present invention is an improvement over ceramic burner heads of the type described particularly in application Ser. No. 134,797 in which the burner head is formed over the entire length of the ceramic body, which is generally of rectangular parallelepipedal configuration, with mutually parallel slit-like flow passages for the fuel and oxidizing agent and in which the passages for the fuel alternate with those of the oxidizing agent and the passages for the different fluids are separated from one another by partitions which are composed of fluid-permeable porous material.
Ceramic burner heads of this type can be introduced individually or in stacks or arrays, in furnaces and other heating installations of small capacity or in large-capacity industrial furnaces and are suitable for use with gaseous and liquid fuels.
As described in the application Ser. No. 134,797, now U.S. Pat. No. 4,376,627, at least for liquid fuels, it is advantageous to preheat the oxidizing agent by indirect heat exchange with furnace exhaust gases, and then to effect a further heat exchange between the oxidizing agent and the liquid fuel in the flow passages of the ceramic body.
The liquid fuel penetrates the porous walls between the flow passages in the region of the burner mouth and is entrained by the combustion air which has been preheated in the manner described. Because the fuel evaporates on or in the porous walls and the high effective surface area thereof in a rapid manner and because of the cooling effect of the evaporation, an overheating of the fuel, which could lead to cracking, cannot occur. In the air passages, the air and the fuel mix and the resulting ignitable mixture is discharged.